The purpose of this lab course is to give Master students the opportunity to discover the mechanisms involved in membrane ultrafiltration processes in relation with the rheological behaviour of the aqueous filtered suspensions. During the filtration process under shear flow and pressure forces, the filtered particles accumulate near the membrane surface forming a concentrated layer of a few hundred micrometers. The changes from a dilute phase to a concentrated phase induce a change in the rheological behavior of the suspensions which control the performance of the process. The proposed approach, is to combine the characterisation of the filtration properties of the suspensions, the in-situ visualisation of the accumulated layers and the rheometric behaviour of the suspensions. The goal is to understand the main mechanisms governing the ultrafiltration process used in several industrial applications e.g. bio- and agro-industries, chemical industries, pharmaceutical, nuclear, as well as water and sludge treatment.
This lab-course is well suited to M1 and M2 students having a background in fluid mechanics, chemical engineering, and some knowledge on particles suspensions properties and theirs rheological behaviour.
Mechanisms involved during membrane filtration processes: evolution of the rheological properties of aqueous suspensions with increasing concentrations
8 hrs session
Aqueous clay or cellulose nanocrystal suspensions, composed of nanometric sized particles (a few nm in diameter and hundreds nanometer in length) will be studied in a cross flow membrane ultrafiltration facility. This ultrafiltration set-up will allow to characterize the filtration properties of the suspensions (permeation flux) as a function of time and external applied forces (transmembrane pressure and cross flow).
Simultaneously the velocity field will be observed inside the filtration canal in the accumulated layers above the membrane, thanks to micro-particle image velocimetry. In parallel, the rheological behavior of the suspensions will be characterized as a function of the particles concentrations, thanks to rheometric measurements. Theoretical modelling of the ultrafiltration process will be addressed to highlight the link between the rheological behavior and the filtration performance.